Much of the world depends on annual snowmelt to provide fresh water coming down out of the mountains to fill up rivers and lakes. In many cases, this snowmelt water is stored for use by local residents throughout the rest of the year.
Unfortunately, a new study suggests that snowmelt is likely to decline at several locations throughout the northern hemisphere, including major drainage basins in in Northern and Central California, and the basins associated with the Colorado and Rio Grande rivers in the Southwest U.S.
Earth scientist Justin Mankin and team published their research last week (November 12th) in the academic journal Environmental Research Letters.
As highlighted by ValueWalk this week, another recently published study study argues that there is a limited supply of “modern groundwater” accessible to humans, as the vast majority of deeper groundwater in the planetary crust is older and too contaminated for use by humans.
New study on snowmelt in the Northern Hemisphere
Dr. Justin S. Mankin, from Columbia University, and his co-researchers studied 421 drainage basins in the Northern Hemisphere that are filled by rainfall and snowmelt, and then applied the data to several different climate models.
They discovered that 97 drainage basins, that two billion people use for water, are highly dependent on snowmelt. The bad news is the likelihood that the basins will receive less snow over the next 100 years was just over 67%.
The research highlights that most snowmelt-dependent basins in the U.S. are those in Northern and Central California, and the drainage basins of the Colorado and Rio Grande rivers. Globally, the Atlas basin of Morocco and the Ebro-Duero basin, which supplies water to Portugal, Spain and southern France, were also categorized as especially sensitive to changes in snowmelt.
The study provides important information for city water managers as they make decisions about where to draw water from and how much to use. The loss of snow may also require cities and farmers to find more efficient irrigation methods, to recycle water and to grow fewer water-intensive crops.
“Water managers need to prepare themselves for the worst outcome,” Mankin commented, and went on to note the general public can help save life-giving snowpacks by limiting contributions of greenhouse gases.
Abstract from new snowmelt study
We identify the NH basins where present spring and summer snowmelt has the greatest potential to supply the human water demand that would otherwise be unmet by instantaneous rainfall runoff. Using a multi-model ensemble of climate change projections, we find that these basins—which together have a present population of ~2 billion people—are exposed to a 67% risk of decreased snow supply this coming century. Further, in the multi-model mean, 68 basins (with a present population of >300 million people) transition from having sufficient rainfall runoff to meet all present human water demand to having insufficient rainfall runoff. However, internal climate variability creates irreducible uncertainty in the projected future trends in snow resource potential, with about 90% of snow-sensitive basins showing potential for either increases or decreases over the near-term decades. Our results emphasize the importance of snow for fulfilling human water demand in many NH basins, and highlight the need to account for the full range of internal climate variability in developing robust climate risk management decisions.